The present invention relates to a semiconductor integrated circuit having a nonvolatile memory in which characteristic degradation is caused by repetitive rewriting, and to a technique effective when applied to, for example, a microcomputer.
Japanese Unexamined Patent Publication No. 2001-306543 discloses a technique in which data such as a user program is written in a user memory area in a flash memory, default flash firmware, parameters, and flash identification information are pre-stored in a mask memory area in a mask ROM, version information, lot information, or the like is stored in a nonvolatile memory, and a CPU selects and executes the optimum flash firmware and parameters on the basis of the version information, thereby performing a process of rewriting the flash memory under optimum conditions.
Japanese Unexamined Patent Publication No. 2002-245023 discloses a technique in which an EEPROM for data and an EEPROM for program are provided, a lock code is stored in a designated area, and the possibility of falsification on money data and a program stored in a rewritable memory such as the EEPROM for data and the EEPROM for program is suppressed by using the lock code.